The present invention relates to mechanical machining techniques, and more particularly, to an electrochemical discharge machining device capable of performing a discharge machining as well as an electrolytic machining in the same device, and a machining method. More specifically, the present invention relates to an electrochemical discharge machining device and a machining method for performing an electrolytic machining of a tool fed by a three-dimensional tool feeder which can accurately feed a tool in three dimensions in a current controlled mode, regulate a concentration and a height of an electrolyte, and perform an electrochemical discharge machining of a workpiece using the machined tool in a voltage controlled mode.
Traditional mechanical machining techniques for machining workpieces have included physical processes involving a lathe or milling. However, to perform machining of precision parts or easily breakable materials of high hardness, various machining devices and methods have been devised. Machining techniques which can perform machining using electrical and chemical principles include electrolytic machining and a discharge machining.
As for electrolytic machining, when a current is applied to the workpiece (which serves as an anode) immersed in an alkaline electrolyte and a tool (which serves as a cathode), the workpiece can be machined through the generated electrical and chemical reactions. Electrolytic polishing and electrolytic grinding are examples of such processes.
The workpiece is slowly dissolved in the electrolyte through an oxidation reaction. As such, by adjusting an applied current density, the extent and rate of dissolving may be controlled. Such electrolytic machining can be easily performed for metal materials with low carbon contents. Thus, heat resistant steel, cemented carbide, and high-tensile steel, which are difficult to machine by physical processes because of their higher strength and lower carbon contents as compared with an iron metal material, can be machined.
On the other hand, high hardness non-metallic materials have been conventionally machined using diamond powder. Yet, this method requires a long time period for machining, as well as the use of expensive diamond powder.
Alternatively, to machine such materials a discharge machining process has been developed. In discharge machining a negative voltage is applied to the workpiece and a positive voltage is applied to the tool. Then, when two materials are brought together at distance of a few of xcexcm, sparking (i.e., dielectric breakdown) occurs. This event is referred to as discharge, which is used for machining the workpiece.
Conventional electrolytic machining and discharge machining are special machining techniques which use different methods and different devices. However, research to provide electrolytic machining and discharge machining in the same device has been carried out in recent years, which is commonly referred to as an electrochemical discharge machining.
A typical workpiece subjected to conventional electrochemical discharge machining would include a non-metallic material having high hardness, which is subjected to discharge machining as described above. The non-metallic high hardness materials are utilized in fields requiring high accuracy, such as aerospace, precious metal processing, and automobiles. In the conventional electrochemical discharge machining device, the tool is machined in a separate machining device, and then used for machining the non-metallic materials with high hardness.
In spite of developments improving the accuracy of machining, the workpiece often cannot be accurately machined due to frequent desorption of the tool. Further, such conventional electrochemical discharge machining processes developed for the unified process of electrolytic machining and discharge machining is disadvantageous in that the processes are complicated, and the tool is machined by a separate device.
Accordingly, it is an object of the present invention to alleviate the above noted problems and to provide an electrochemical discharge machining device that is capable of simultaneously performing an electrolytic machining and a discharge machining, thereby decreasing machining errors.
According to one aspect of the present invention an electrochemical discharge machining device may include a three-dimensional tool feeder or means, a position controller for electrically controlling movements of the three-dimensional tool feeder, and a tool fixed at a lower portion of the three-dimensional tool feeder. The device may also include an electrode having an opposite polarity to the tool, a power controller electrically connected to the position controller for applying a current to the tool and the electrode, and an electrolyte for promoting a certain electrochemical reaction between the tool and the electrode immersed therein. Furthermore, an electrolytic bath including the electrolyte in which a workpiece is processed may be included and may also include a jig by which the workpiece is upwardly positioned apart from a bottom of the bath.
More particularly, the electrolyte may be an aqueous alkaline solution selected from the group consisting of potassium hydroxide, magnesium hydroxide, sodium hydroxide, and calcium hydroxide. The tool may be made of a metal material including at least one of tungsten and copper. Additionally, the electrode may include at least one of platinum, silver and gold. Also, the workpiece may include at least one of glass, ceramic, quartz, diamond, ruby, and sapphire.
In addition, the electrolytic bath may include an exhaust valve for removing the electrolyte outside thereof, which may be at the bottom of one side of the bath, for example. The electrochemical discharge machining device may further include an electrolyte-supplying tank for supplying the electrolyte to the electrolytic bath. Moreover, the electrolyte-supplying tank may include a supply valve for regulating the flow of electrolyte to the electrolytic bath, which may be at a bottom side of the tank, for example.
A method aspect of the invention is for an electrochemical discharge machining method and may include supplying an electrolyte to an electrolytic bath at a predetermined height, immersing a tool at a length to be machined into the electrolyte, and electrolytically machining the tool by applying an electric field in a current controlled mode such that the tool and the electrode serve as an anode and a cathode, respectively. Furthermore, a concentration and a height of the electrolyte may be regulated based upon the material used for the workpiece, and an electric field may be applied in a voltage controlled mode so that the tool and the electrode serve as a cathode and an anode, respectively. Additionally, the tool may be fed to the workpiece to perform an electrochemical discharge machining.
Further, the electrolyte may be an aqueous alkaline solution selected from the group consisting of potassium hydroxide, magnesium hydroxide, sodium hydroxide, and calcium hydroxide. Also, the workpiece may include at least one of glass, ceramic, quartz, diamond, ruby, and sapphire. The tool may be made of a metal including at least one of tungsten and copper. Also, the electrode may be made of a material including at least one of platinum, silver and gold.
Further, the electrolytic bath may include an exhaust valve for removing the electrolyte to the outside thereof, for example, at the bottom of one side of the bath. Additionally, an electrolyte-supplying tank may be used for supplying the electrolyte to the electrolytic bath. The electroyte-supplying tank may be spaced apart from the bottom of the bath at a predetermined height and positioned over one side of the bath. Also, the electrolyte-supplying tank may include a supply valve for supplying the electrolyte to the electrolytic bath, e.g., at a bottom side of the tank.